An eye chart is a tool used by eye care professionals to measure visual acuity, which is the clarity or sharpness of vision. The most common type is the Snellen chart, featuring rows of letters that decrease in size. Patients read the letters from a specific distance, usually 20 feet, to determine how well they can see. Eye charts can also include symbols or pictures for those who cannot read letters, such as children or individuals with language barriers. The results help diagnose vision problems and guide treatment options, ensuring that patients receive appropriate care for their eyesight.